STB is a solid puller so heed his words. The only thing I question is the quad dominance thing because I think at your strength level EVERYTHING needs to come up but more glute/ham work is always a good thing.
The only other thing I would add is the whole throw your arms up before you pull thing isn't helping.
FWIW you need to consciously pull your shoulders down (not forward) towards your hips and get your lats tight and chest up before you pull. From what I see, you don't set your lats at all and this is a problem.
Your starting position would change just by virtue of doing these two things (set your lats and raise your chest.)